It's an impressive, quietly powerful film that will stay with you long after the final credits roll.

The film just isn't biting enough to make Warner a mascot for the race-based injustice that pervades the American criminal justice system.

The sole fresh twist, one that should have been more than enough to drive the show - one friend dedicating his life to exonerating the other - is repeatedly undermined by their unequal presentation.

Through a tipped balance of actions over words, the forlorn eyes and slight frame of Lakeith Stanfield present a beleaguered stature that is nothing short of heartbreaking at every turn and every passing year behind bars.